1. Field of the Invention
The present invention relates to a heat exchanger of the tube-fin type for use, in particular but not exclusively, as an evaporator in an automobile air conditioning system.
2. Discussion of the Prior Art
Conventionally, a heat exchanger of the tube-fin type for use as an evaporator or condensor includes a plurality of U-shaped heat exchange tubes on which are arranged a large number of thin metal fins. The heat exchange tubes are connected via inlet and outlet manifolds comprising a plurality of tubular connections, to a coolant fluid inlet or outlet or are connected to return bends, whereby a circulatory path or paths for coolant is defined between the inlet and the outlet.
As an alternative to providing separate return bend connections and manifolds the heat exchange tubes can be connected to a connecting tank or end tank which is provided with an inlet and outlet for connection to the coolant circuit, and which it internally divided so as to define with the heat exchange tubes the circulatory path or paths for the fluid between a fluid inlet and outlet. The heat exchange tubes are connected to the end tank through projecting tubular stubs provided on the end tank which are received within end portions of the heat exchange tubes, an adhesive, or other synthetic hardenable material, being employed to seal the connection. A heat exchanger of this kind is known from British Patent No 1601429. During assembly, recesses defined around the projecting tubular connections are provided with the hardenable material, into which ends of the heat exchange tubes are inserted. A clearance is provided between the projecting tubular connections and heat exchange tubes to allow penetration of hardenable material therebetween.
It is also known to solder or braze the ends of the heat exchange tubes to the projecting stubs.
A drawback of a soldered or brazed joint, or joint employing adhesive or hardenable material is that such joints are susceptible to leakage. Such joints are also liable to become internally restricted or clogged as sealing material enters the tube. When soldering is employed, there are obvious safety risks associated with this technique. These joints are also relatively expensive to produce.